Carbon monoxide (CO) and carbon dioxide (CO2) emissions can accumulate when a vehicle operates at extended speed controlled conditions, for example at idle speed, in an enclosed environment. Oxygen (O2) is involved in combustion reactions that produce CO and CO2, and both are emitted from an exhaust tailpipe. As these concentrations increase, the engine may begin to act like an exhaust gas recirculation system (EGR), taking in higher concentrations of CO and CO2 via the intake manifold.
A method for detecting CO is described in U.S. Pat. No. 5,333,703, wherein the vehicle includes cabin and external CO sensors. When the sensors detect a predetermined maximum carbon oxide threshold of CO, the engine can be disabled if the vehicle is in neutral or park mode.
However, CO sensors present an additional cost in the manufacturing of a vehicle. In contrast, the subject application presents a low-cost, or even no-cost, solution for estimating O2, CO, and CO2 concentrations when the engine is in extended speed controlled conditions.
A method for detection of emissions levels during extended engine speed controlled operation is provided. The method includes monitoring mass airflow passing through the engine while operating the engine. The method further includes adjusting mass airflow responsive to engine speed to maintain a desired engine speed. The method further includes shutting down the engine when engine mass airflow becomes higher than a predetermined mass airflow threshold.
By using an airflow sensor, such as an air meter, in the intake manifold of an engine, O2 concentration, CO concentration, and CO2 concentration (herein referred to as [O2], [CO], and [CO2]) may be estimated. A mass airflow increase during extended operation of an engine under speed controlled conditions (e.g., engine idle speed) indicates a decrease in intake [O2]; that is, as the engine seeks to achieve stoichiometric conditions for combustion in a reduced [O2] situation, a request to increase mass airflow to the engine is executed. Using predetermined relationships between at least mass airflow rate, engine power, [CO2], [CO], and [O2], concentrations of these constituent gases may be estimated. Thus, when concentration of one or more constituent gases exceeds a predetermined maximum carbon oxide threshold or becomes less than a predetermined minimum oxygen threshold, a method for disabling the engine can be employed.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.